What is the importance of the macronutrients for the human body?

Macronutrients are important for your body mainly because they provide energy, which are counted in calories. Macronutrients are called "macro" not because they are extremely large, but because they are needed in large amounts. The 3 main macronutrients are proteins, carbohydrates, and fats.

Proteins:

Proteins are present in every living cell, and they vary in many different ways. They are made up of amino acid chains, consisting from 20 to several thousands different acids. 9 amino acids are called the "essential" amino acids because the human body cannot produce them on its own so they are necessary to include in the diet. Not only do proteins provide energy, but they also have different jobs such as carrying out chemical reactions or transporting substances throughout the body. Proteins can be found in meats from animals, or in plants like nuts, seeds, or grains. Proteins from animals are called "complete proteins" because they include the essential amino acids, but proteins from plants are called "incomplete proteins" because they lack one or more of the essential amino acids.

Carbohydrates:

Carbohydrates have two main purposes: they are the primary energy source of the body and they are a major source of calories. Carbohydrates come in two different forms, simple carbohydrates and complex carbohydrates. Simple carbohydrates can't be broken down into simpler sugars, and complex carbohydrates are strings of simple carbohydrates. Glucose and glycogen are the forms of carbohydrates that the body uses. The human body can convert both simple and complex carbohydrates into energy very quickly, so carbohydrates are an ideal source of energy. Carbohydrates can be found in grains, cellulose, and fibers.

Fats:
Although people think all fats are detrimental, this is not true. In fact, fats are necessary in order for our body to function properly. Fats contain twice as much energy as carbohydrates, so it is a great source that fuels our daily body work. Although fat is not usually used for immediate use of energy, it is crucial nonetheless. A normal teen's diet should contain between 20 - 35% of fat, but a diabetic's fat percentage should not be over 30. There are good and bad types of fats; Good fats include unsaturated fats, which can be found in vegetable oil. Unsaturated fats bring up HDL, which is a good kind of cholesterol that cleans up your artery and veins. On the other hand, saturated fats and trans fats are bad types of fats. Saturated fat can be found in foods such as dairy and seafood, and trans fats can be found in processed food. Both of these fats bring up LDL (bad cholesterol), which clogs up the artery and veins while lowering HDL, the good cholesterol.